Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Implementation and evaluation of an antimicrobial stewardship programme in companion animal clinics: A stepped-wedge design intervention study
Hopman, Nonke E.M. ; Portengen, Lützen ; Hulscher, Marlies E.J.L. ; Heederik, Dick J.J. ; Verheij, T.J.M. ; Wagenaar, Jaap A. ; Prins, Jan M. ; Bosje, Tjerk ; Schipper, Louska ; Geijlswijk, Ingeborg M. Van; Broens, Els M. - \ 2019
PLoS ONE 14 (2019)11. - ISSN 1932-6203

Background To curb increasing resistance rates, responsible antimicrobial use (AMU) is needed, both in human and veterinary medicine. In human healthcare, antimicrobial stewardship programmes (ASPs) have been implemented worldwide to improve appropriate AMU. No ASPs have been developed for and implemented in companion animal clinics yet. Objectives The objective of the present study was to implement and evaluate the effectiveness of an ASP in 44 Dutch companion animal clinics. The objectives of the ASP were to increase awareness on AMU, to decrease total AMU whenever possible and to shift AMU towards 1st choice antimicrobials, according to Dutch guidelines on veterinary AMU. Methods The study was designed as a prospective, stepped-wedge, intervention study, which was performed from March 2016 until March 2018. The multifaceted intervention was developed using previous qualitative and quantitative research on current prescribing behaviour in Dutch companion animal clinics. The number of Defined Daily Doses for Animal (DDDAs) per clinic (total, 1st, 2nd and 3rd choice AMU) was used to quantify systemic AMU. Monthly AMU data were described using a mixed effect time series model with auto-regression. The effect of the ASP was modelled using a step function and a change in the (linear) time trend. Results A statistically significant decrease of 15% (7%-22%) in total AMU, 15% (5%-24%) in 1st choice AMU and 26% (17%-34%) in 2nd choice AMU was attributed to participation in the ASP, on top of the already ongoing time trends. Use of 3rd choice AMs did not significantly decrease by participation in the ASP. The change in total AMU became more prominent over time, with a 16% (4%-26%) decrease in (linear) time trend per year. Conclusions This study shows that, although AMU in Dutch companion animal clinics was already decreasing and changing, AMU could be further optimised by participation in an antimicrobial stewardship programme.

Herkomst Nutriënten in het landelijk gebied van Schieland
Schipper, Peter ; Gerven, Luuk van; Boekel, Erwin van; Renaud, Leo ; Ros, Gerard - \ 2019
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2969) - 71
De Europese Kaderrichtlijn Water (KRW) schrijft voor dat het oppervlaktewater in 2027 voldoende schoon en ecologisch gezond is. In veel Nederlandse wateren is de nutriëntenbelasting (nog) te hoog om de doelen voor de KRW te halen. Het Hoogheemraadschap van Schieland en de Krimpenerwaard (HHSK) wil ter voorbereiding van besluiten over verbetering van de waterkwaliteit beter inzicht krijgen in de herkomst van de nutriënten in hun wateren. In dit onderzoek is de nutriëntenbelasting van de oppervlaktewateren (en herkomst daarvan) gekwantificeerd voor de periode 2000-2013 voor negen polders in het landelijke gebied van Schieland. Ook zijn effecten van autonoom mestbeleid en enkele landbouwmaatregelen indicatief berekend en zijn de fosfaat- en stikstoftoestand van de toplaag van de landbouwgronden ruimtelijk in kaart gebracht.De nutriëntenbelasting (en herkomst daarvan) in de beschouwde polders verschilt sterk door de grote verschillen in landgebruik, bodemtype en hydrologie. De totale nutriëntenbelasting per hectare is het grootst in polders met veel glastuinbouw, gevolgd door polders met veel akkerbouw. Af- en uitspoeling vanuit landbouwgronden leveren de grootste bijdrage aan de stikstofbelasting (gemiddeld 44%). Dit komt vooral door actuele mestgiften. De rest van de stikstofbelasting komt vooral door diffuse lozingen vanuit glastuinbouw en diffuse bronnen in stedelijk gebied. Af- en uitspoeling leveren ook voor fosfor de grootste bijdrage (gemiddeld 52%). Deze af- en uitspoeling worden niet zozeer door actuele mestgiften bepaald, maar meer door nalevering, historische mestgiften en kwel. De rest van de fosforbelasting komt – net als stikstof – vooral door glastuinbouw en diffuse bronnen in stedelijk gebied. De berekeningen geven aan dat met autonoom mestbeleid en de beschouwde additionele landbouwmaatregelen de nutriëntenbelasting weinig zal afnemen. Wel levert volledige aansluiting van de glastuinbouw een aanzienlijke verlaging van de belasting in de polders met veel glastuinbouw. Dit is al enkele jaren in gang gezet. Vooral in Bleiswijk zal de belasting hierdoor naar verwachting verder afnemen. Trefwoorden: Kaderrichtlijn Water, oppervlaktewater kwaliteit, nutriënten belasting, stikstof, fosfor, herkomst, uitspoeling, afspoeling, bemesting, glastuinbouw, bodemverbetering, kringloopwijzer, fosfaattoestand, stikstof leverend vermogen.
Projecting terrestrial biodiversity intactness with GLOBIO 4
Schipper, Aafke M. ; Hilbers, Jelle P. ; Meijer, Johan R. ; Antão, Laura H. ; Benítez-López, Ana ; Jonge, Melinda M.J. de; Leemans, Luuk H. ; Scheper, Eddy ; Alkemade, Rob ; Doelman, Jonathan C. ; Mylius, Sido ; Stehfest, Elke ; Vuuren, Detlef P. van; Zeist, Willem Jan van; Huijbregts, Mark A.J. - \ 2019
Global Change Biology (2019). - ISSN 1354-1013
anthropocene - biodiversity scenarios - global environmental change - land-use downscaling - mean species abundance

Scenario-based biodiversity modelling is a powerful approach to evaluate how possible future socio-economic developments may affect biodiversity. Here, we evaluated the changes in terrestrial biodiversity intactness, expressed by the mean species abundance (MSA) metric, resulting from three of the shared socio-economic pathways (SSPs) combined with different levels of climate change (according to representative concentration pathways [RCPs]): a future oriented towards sustainability (SSP1xRCP2.6), a future determined by a politically divided world (SSP3xRCP6.0) and a future with continued global dependency on fossil fuels (SSP5xRCP8.5). To this end, we first updated the GLOBIO model, which now runs at a spatial resolution of 10 arc-seconds (~300 m), contains new modules for downscaling land use and for quantifying impacts of hunting in the tropics, and updated modules to quantify impacts of climate change, land use, habitat fragmentation and nitrogen pollution. We then used the updated model to project terrestrial biodiversity intactness from 2015 to 2050 as a function of land use and climate changes corresponding with the selected scenarios. We estimated a global area-weighted mean MSA of 0.56 for 2015. Biodiversity intactness declined in all three scenarios, yet the decline was smaller in the sustainability scenario (−0.02) than the regional rivalry and fossil-fuelled development scenarios (−0.06 and −0.05 respectively). We further found considerable variation in projected biodiversity change among different world regions, with large future losses particularly for sub-Saharan Africa. In some scenario-region combinations, we projected future biodiversity recovery due to reduced demands for agricultural land, yet this recovery was counteracted by increased impacts of other pressures (notably climate change and road disturbance). Effective measures to halt or reverse the decline of terrestrial biodiversity should not only reduce land demand (e.g. by increasing agricultural productivity and dietary changes) but also focus on reducing or mitigating the impacts of other pressures.

Evaluating the ecological realism of plant species distribution models with ecological indicator values
Hellegers, Marjon ; Ozinga, Wim A. ; Hinsberg, Arjen ; Huijbregts, Mark A.J. ; Hennekens, Stephan M. ; Schaminée, Joop H.J. ; Dengler, Jürgen ; Schipper, Aafke M. - \ 2019
Ecography (2019). - ISSN 0906-7590
BioScore - ecological niche model - Ellenberg indicator values - model selection - scale dependency - validation

Species distribution models (SDMs) are routinely applied to assess current as well as future species distributions, for example to assess impacts of future environmental change on biodiversity or to underpin conservation planning. It has been repeatedly emphasized that SDMs should be evaluated based not only on their goodness of fit to the data, but also on the realism of the modeled ecological responses. However, possibilities for the latter are hampered by limited knowledge on the true responses as well as a lack of quantitative evaluation methods. Here we compared modeled niche optima obtained from European-scale SDMs of 1476 terrestrial vascular plant species with empirical ecological indicator values indicating the preferences of plant species for key environmental conditions. For each plant species we first fitted an ensemble SDM including three modeling techniques (GLM, GAM and BRT) and extracted niche optima for climate, soil, land use and nitrogen deposition variables with a large explanatory power for the occurrence of that species. We then compared these SDM-derived niche optima with the ecological indicator values by means of bivariate correlation analysis. We found weak to moderate correlations in the expected direction between the SDM-derived niche optima and ecological indicator values. The strongest correlation occurred between the modeled optima for growing degree days and the ecological indicator values for temperature. Correlations were weaker for SDM-derived niche optima with a more distal relationship to ecological indicator values (notably precipitation and soil moisture). Further, correlations were consistently highest for BRT, followed by GLM and GAM. Our method gives insight into the ecological realism of modeled niche optima and projected core habitats and can be used to improve SDMs by making a more informed selection of environmental variables and modeling techniques.

Suiker in drinkpakjes: Chocomel spant de kroon
Vet, Emely de - \ 2019
The science base of a strategic research agenda - Executive Summary
Bray, A.W. ; Kim, J.H. ; Schrumpf, M. ; Peacock, C. ; Banwart, S. ; Schipper, L. ; Angers, D. ; Chirinda, N. ; Lopes Zinn, Y. ; Albrecht, A. ; Kuikman, P.J. ; Jouquet, P. ; Demenois, J. ; Farrell, M. ; Fontaine, S. ; Soussana, J.F. ; Kuhnert, M. ; Milne, E. ; Taghizadeh-Toosi, A. ; Cerri, C.E.P. ; Corbeels, M. ; Cardinael, R. ; Alcántara Cervantes, V. ; Olesen, J.E. ; Batjes, N.H. ; Heuvelink, G.B.M. ; Maia, S.M.F. ; Keesstra, S.D. ; Claessens, L.F.G. ; Madari, B.E. ; Verchot, L. ; Nie, W. - \ 2019
EU - 16 p.
A summary presenting the challenges for soil carbon sequestration research, hypotheis to be further tested and key research (and innvation) products.
How to measure, report and verify soil carbon change to realize the potential of soil carbon sequestration for atmospheric greenhouse gas removal
Smith, Pete ; Soussana, Jean Francois ; Angers, Denis ; Schipper, Louis ; Chenu, Claire ; Rasse, Daniel P. ; Batjes, Niels H. ; Egmond, Fenny van; McNeill, Stephen ; Kuhnert, Matthias ; Arias-Navarro, Cristina ; Olesen, Jorgen E. ; Chirinda, Ngonidzashe ; Fornara, Dario ; Wollenberg, Eva ; Álvaro-Fuentes, Jorge ; Sanz-Cobena, Alberto ; Klumpp, Katja - \ 2019
Global Change Biology (2019). - ISSN 1354-1013
measurement - monitoring - MRV - reporting - soil organic carbon - soil organic matter - verification

There is growing international interest in better managing soils to increase soil organic carbon (SOC) content to contribute to climate change mitigation, to enhance resilience to climate change and to underpin food security, through initiatives such as international ‘4p1000’ initiative and the FAO's Global assessment of SOC sequestration potential (GSOCseq) programme. Since SOC content of soils cannot be easily measured, a key barrier to implementing programmes to increase SOC at large scale, is the need for credible and reliable measurement/monitoring, reporting and verification (MRV) platforms, both for national reporting and for emissions trading. Without such platforms, investments could be considered risky. In this paper, we review methods and challenges of measuring SOC change directly in soils, before examining some recent novel developments that show promise for quantifying SOC. We describe how repeat soil surveys are used to estimate changes in SOC over time, and how long-term experiments and space-for-time substitution sites can serve as sources of knowledge and can be used to test models, and as potential benchmark sites in global frameworks to estimate SOC change. We briefly consider models that can be used to simulate and project change in SOC and examine the MRV platforms for SOC change already in use in various countries/regions. In the final section, we bring together the various components described in this review, to describe a new vision for a global framework for MRV of SOC change, to support national and international initiatives seeking to effect change in the way we manage our soils.

Effect on BMI of a multi-component treatment with E-modules for 3–8-year-old obese children
Hoek, Esther Van; Feskens, Edith J.M. ; Bouwman, Laura I. ; Verburgt, Wilma H. ; Jager, Wilco De; Schipper, Henk S. ; Vrijkotte, Tanja G.M. ; Janse, Arieke J. - \ 2019
Child and Adolescent Obesity 2 (2019)1. - ISSN 2574-254X - p. 79 - 95.
Introduction: Childhood obesity has serious health risks including the development of metabolic syndrome, cardiovascular disease and mortality later in life. The critical growth period from 3 to 7 years provides a window of opportunity for interventions. The goal of this study is to evaluate a one year, multidisciplinary, low-intensity treatment program for young obese children, complemented with web-based modules, called “AanTafel!”, on body composition, cardiometabolic risk profile, quality of life (HRQoL), eating behavior and physical activity.
Methods: In the pre-post-test design all measures were taken at baseline, 4 months, at the end of treatment and 3 years after baseline.
Results: Thirteen boys and 27 girls with median BMI z-score of, respectively, 4.2 and 3.3 aged 3 to 8 started “AanTafel!”. Eighty percent (n = 32) completed treatment. BMI z-score decreased with 0.45 (end of treatment) and sustained after 3 years. At the start, 16.7% of the children had all four components of metabolic syndrome which decreased to 0%. HDL cholesterol significantly increased. Concentrations of the markers IL18, e-selectin, and sICAM significantly decreased indicating a reduction of inflammation.
Conclusion: “AanTafel!” is effective in improving health of obese young children. The reduction of overweight is clinically relevant and sustained after 3 years
Visualizing trypanosomes in a vertebrate host reveals novel swimming behaviours, adaptations and attachment mechanisms
Dóró, Éva ; Jacobs, Sem H. ; Hammond, Ffion R. ; Schipper, Henk ; Pieters, Remco P.M. ; Carrington, Mark ; Wiegertjes, Geert F. ; Forlenza, Maria - \ 2019
eLife 8 (2019). - ISSN 2050-084X
host-pathogen interaction - infectious disease - microbiology - swimming behavior - Trypanosoma carassii - zebrafish

Trypanosomes are important disease agents of humans, livestock and cold-blooded species, including fish. The cellular morphology of trypanosomes is central to their motility, adaptation to the host's environments and pathogenesis. However, visualizing the behaviour of trypanosomes resident in a live vertebrate host has remained unexplored. In this study, we describe an infection model of zebrafish (Danio rerio) with Trypanosoma carassii. By combining high spatio-temporal resolution microscopy with the transparency of live zebrafish, we describe in detail the swimming behaviour of trypanosomes in blood and tissues of a vertebrate host. Besides the conventional tumbling and directional swimming, T. carassii can change direction through a 'whip-like' motion or by swimming backward. Further, the posterior end can act as an anchoring site in vivo. To our knowledge, this is the first report of a vertebrate infection model that allows detailed imaging of trypanosome swimming behaviour in vivo in a natural host environment.

Exploring the functional role of the digital mucus glands and their secretions in tree frog attachment
Langowski, J.K.A. ; Singla, Saranshu ; Nyarko, Alex ; Schipper, H. ; Berg, Frank van den; Kaur, Sukhmanjot ; Astley, Henry C. ; Gussekloo, S.W.S. ; Dhinojwala, Ali ; Leeuwen, J.L. van - \ 2019
- 1 p.
Comparative and functional analysis of the digital mucus glands and secretions of tree frogs
Langowski, Julian K.A. ; Singla, Saranshu ; Nyarko, Alex ; Schipper, Henk ; Berg, Frank T. van den; Kaur, Sukhmanjot ; Astley, Henry C. ; Gussekloo, Sander W.S. ; Dhinojwala, Ali ; Leeuwen, Johan L. Van - \ 2019
Frontiers in Zoology 16 (2019). - ISSN 1742-9994
Cryo-histochemistry - Hyla cinerea - Infrared spectroscopy - Lubrication - Macrogland - Mucosubstance - Sum frequency generation spectroscopy - Synchrotron micro-computer-tomography - Wet adhesion

Background: Mucus and mucus glands are important features of the amphibian cutis. In tree frogs, the mucus glands and their secretions are crucial components of the adhesive digital pads of these animals. Despite a variety of hypothesised functions of these components in tree frog attachment, the functional morphology of the digital mucus glands and the chemistry of the digital mucus are barely known. Here, we use an interdisciplinary comparative approach to analyse these components, and discuss their roles in tree frog attachment.

Results: Using synchrotron micro-computer-tomography, we discovered in the arboreal frog Hyla cinerea that the ventral digital mucus glands differ in their morphology from regular anuran mucus glands and form a subdermal gland cluster. We show the presence of this gland cluster also in several other - not exclusively arboreal - anuran families. Using cryo-histochemistry as well as infrared and sum frequency generation spectroscopy on the mucus of two arboreal (H. cinerea and Osteopilus septentrionalis) and of two terrestrial, non-climbing frog species (Pyxicephalus adspersus and Ceratophrys cranwelli), we find neutral and acidic polysaccharides, and indications for proteinaceous and lipid-like mucus components. The mucus chemistry varies only little between dorsal and ventral digital mucus in H. cinerea, ventral digital and abdominal mucus in H. cinerea and O. septentrionalis, and between the ventral abdominal mucus of all four studied species.

Conclusions: The presence of a digital mucus gland cluster in various anuran families, as well as the absence of differences in the mucus chemistry between arboreal and non-arboreal frog species indicate an adaptation towards generic functional requirements as well as to attachment-related requirements. Overall, this study contributes to the understanding of the role of glands and their secretions in tree frog attachment and in bioadhesion in general, as well as the evolution of anurans.

ICON.NL: coastline observatory to examine coastal dynamics in response to natural forcing and human interventions
Aarninkhof, Stefan ; Schipper, Matthieu De; Luijendijk, Arjen ; Ruessink, Gerben ; Bierkens, Marc ; Wijnberg, Kathelijne ; Roelvink, Dano ; Limpens, J. ; Baptist, M.J. ; Riksen, Michel ; Bouma, Tjeerd ; Vries, Sierd de; Reniers, Ad ; Hulscher, Suzanne ; Wijdeveld, Arjan ; Dongeren, Ap van; Gelder-Maas, Carola van; Lodder, Quirijn ; Spek, Ad van der - \ 2019
- 8 p.
In the light of challenges raised by a changing climate and increasing population pressure in coastal regions, it has become clear that theoretical models and scattered experiments do not provide the data we urgently need to understand coastal conditions and processes. We propose a Dutch coastline observatory named ICON.NL, based at the Delfland Coast with core observations focused on the internationally well-known Sand Engine experiment, as part of an International Coastline Observatories Network (ICON). ICON.NL will cover the physics and ecology from deep water to the dunes. Data will be collected continuously by novel remote sensing and in-situ sensors, coupled to numerical models to yield unsurpassed long-term coastline measurements. The combination of the unique site and ambitious monitoring design enables new avenues in coastal science and a leap in interdisciplinary research.
Potential of novel desert microalgae and cyanobacteria for commercial applications and CO2 sequestration
Schipper, Kira ; Muraikhi, Mariam Al; Alghasal, Ghamza Saed H.S. ; Saadaoui, Imen ; Bounnit, Touria ; Rasheed, Rihab ; Dalgamouni, Tasneem ; Jabri, Hareb Mohammed S.J. Al; Wijffels, René H. ; Barbosa, Maria J. - \ 2019
Journal of Applied Phycology 31 (2019)4. - ISSN 0921-8971 - p. 2231 - 2243.
Carbon capture - CO - Cyanobacteria - Microalgae - Thermotolerance
CO2 fixation by phototrophic microalgae and cyanobacteria is seen as a possible global carbon emissions reducer; however, novel microalgae and cyanobacterial strains with tolerance to elevated temperatures and CO2 concentrations are essential for further development of algae-based carbon capture. Four novel strains isolated from the Arabian Gulf were investigated for their thermotolerance and CO2-tolerance, as well as their carbon capture capability. Two strains, Leptolyngbya sp. and Picochlorum sp., grew well at 40 °C, with productivities of 106.6 ± 10.0 and 87.5 ± 2.1 mg biomass L−1 d−1, respectively. Tetraselmis sp. isolate showed the highest biomass productivity and carbon capture rate of 157.7 ± 10.3 mg biomass L−1 d−1 and 270.8 ± 23.9 mg CO2 L−1 d−1, respectively, both at 30 °C. Under 20% CO2, the biomass productivity increased over 2-fold for both Tetraselmis and Picochlorum isolates, to 333.8 ± 41.1 and 244.7 ± 29.5 mg biomass L−1 d−1. These two isolates also presented significant amounts of lipids, up to 25.6 ± 0.9% and 28.0 ± 2.0% (w/w), as well as presence of EPA and DHA. Picochlorum sp. was found to have a suitable FAME profile for biodiesel production. Both Tetraselmis and Picochlorum isolates showed promising characteristics, making them valuable strains for further investigation towards commercial applications and CO2 capture.
Partial replacement of red and blue by green light increases biomass and yield in tomato
Kaiser, E. ; Weerheim, C. ; Schipper, R. ; Dieleman, J.A. - \ 2019
Scientia Horticulturae 249 (2019). - ISSN 0304-4238 - p. 271 - 279.
Light spectrum; Green light; Light use efficiency; Solanum lycopersicum
Effects of green light on plant growth are relatively understudied, and published results are contradictory. Although per unit leaf area, green light drives photosynthesis less efficiently than does red light, on a whole-plant level green light may increase growth due to changes in vertical light distribution, leaf light acclimation and canopy architecture. As most studies were conducted on small plants with compact stems, positive effects may have remained unnoticed. In a greenhouse experiment, a tomato (Solanum lycopersicum) crop was exposed to 7, 20 or 39% of green light in a background of narrow bandwidth red and blue light, as well as sunlight, for 76 days. The intensity supplied by lamps (171 μmol m−2 s−1) and the red:blue ratio were similar between treatments. Adding green light (+32%) to the spectrum significantly and linearly increased plant biomass and yield (+6.5%). With increasing green light percentage, there were tendencies for linear increases in leaf biomass (P = 0.06), specific leaf area (P = 0.09), stem biomass (P = 0.07), stem length (P = 0.05) and number of internodes (P = 0.05). In the top and middle leaf layers of the canopy, net photosynthesis rate, stomatal conductance and leaf thickness were unaffected by the treatment while in leaves in the middle leaf layer, chlorophyll a:b ratio and carotenoid concentrations increased with the percentage of green light. This study shows that partial replacement of red by green light increases growth of plants in dense canopies and suggests that the combined effects of a light spectrum on plant growth are more than the sum of wavelength effects on photosynthetic efficiency.
Adding Blue to Red Supplemental Light Increases Biomass and Yield of Greenhouse-Grown Tomatoes, but Only to an Optimum
Kaiser, M.E. ; Ouzounis, Theoharis ; Giday, Habtamu ; Schipper, R. ; Heuvelink, E. ; Marcelis, L.F.M. - \ 2019
Frontiers in Plant Science 9 (2019). - ISSN 1664-462X - 11 p.
LED, biomass, blue light, red light, photosynthesis, tomato, greenhouse, yield
Greenhouse crop production in northern countries often relies heavily on supplemental lighting for year-round yield and product quality. Among the different spectra used in supplemental lighting, red is often considered the most efficient, but plants do not develop normally when grown solely under monochromatic red light (“red light syndrome”). Addition of blue light has been shown to aid normal development, and typical lighting spectra in greenhouse production include a mixture of red and blue light. However, it is unclear whether sunlight, as part of the light available to plants in the greenhouse, may be sufficient as a source of blue light. In a greenhouse high-wire tomato (Solanum lycopersicum), we varied the percentage of blue supplemental light (in a red background) as 0, 6, 12, and 24%, while keeping total photosynthetically active radiation constant. Light was supplied as a mixture of overhead (99 μmol m-2 s-1) and intracanopy (48 μmol m-2 s-1) LEDs, together with sunlight. Averaged over the whole experiment (111 days), sunlight comprised 58% of total light incident onto the crop. Total biomass, yield and number of fruits increased with the addition of blue light to an optimum, suggesting that both low (0%) and high (24%) blue light intensities were suboptimal for growth. Stem and internode lengths, as well as leaf area, decreased with increases in blue light percentage. While photosynthetic capacity increased linearly with increases in blue light percentage, photosynthesis in the low blue light treatment (0%) was not low enough to suggest the occurrence of the red light syndrome. Decreased biomass at low (0%) blue light was likely caused by decreased photosynthetic light use efficiency. Conversely, decreased biomass at high (24%) blue light was likely caused by reductions in canopy light interception. We conclude that while it is not strictly necessary to add blue light to greenhouse supplemental red light to obtain a functional crop, adding some (6–12%) blue light is advantageous for growth and yield while adding 24% blue light is suboptimal for growth.
PCLake+ : A process-based ecological model to assess the trophic state of stratified and non-stratified freshwater lakes worldwide
Janssen, Annette B.G. ; Teurlincx, Sven ; Beusen, Arthur H.W. ; Huijbregts, Mark A.J. ; Rost, Jasmijn ; Schipper, Aafke M. ; Seelen, Laura M.S. ; Mooij, Wolf M. ; Janse, Jan H. - \ 2019
Ecological Modelling 396 (2019). - ISSN 0304-3800 - p. 23 - 32.
Deep lake - Food web model - Lake ecology - Limnology - Shallow lake - Thermal stratification

The lake ecosystem model PCLake is a process-based model that was developed to simulate water quality based on ecological interactions in shallow, non-stratifying lakes in the temperate climate zone. Here we present PCLake+, which extends the PCLake model to cover a wide range of freshwater lakes that differ in stratification regime and climate-related processes. To this end, the model was extended with a hypolimnion layer that can be invoked and configured by forcing functions or by simple built-in empirical relationships that impose stratification. Further adjustments to the original PCLake model have been made with respect to the calculation of 1) light irradiation in the water column, 2) evaporation processes and 3) phenology of macrophytes. The simulation output of PCLake+ for different types of lakes complies well with generally accepted limnological knowledge, thus holding promise for future contributions to ecological theory and application to lakes around the globe.

Bronnenanalyse nutriënten stroomgebied Maas
Schipper, Peter ; Renaud, Leo ; Boekel, Erwin van - \ 2019
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2931) - 81
De waterkwaliteit in Nederland – en ook in het Maasstroomgebied (Noord-Brabant en Limburg) – verbetert wel, maar dit gaat niet snel genoeg om de doelen die voor de Europese Kaderrichtlijn Water (KRW) zijn gesteld op tijd te halen. De stoffen stikstof en fosfor (nutriënten) zijn belangrijke factoren voor het bereiken van waterkwaliteitsdoelen. Om effectieve maatregelen te vinden, zijn gedegen gebiedsgerichte analyses nodig om bronnen van de belasting van het (grond)watermilieu door stoffen te kwantificeren. Deze analyses vormen de basis voor de maatregelen die in 2021 worden vastgesteld in de nationale stroomgebiedbeheerplannen (derde generatie SGBP’en) en regionale (water)plannen. De waterschappen en provincies in het Maasstroomgebied hebben behoefte aan een eenduidige analyse van de herkomst van de nutriënten in het oppervlaktewater. In opdracht van het Programmabureau KRW-DHZ Maasregio is onderzoek uitgevoerd naar de nutriëntenbelasting en de bronnen die deze belasting veroorzaken. Uit het onderzoek blijkt dat de totale nutriëntenbelasting van het oppervlaktewater in hoofdzaak worden bepaald door de diffuse uit- en afspoeling vanuit landbouwgronden, effluenten van rioolwaterzuiveringsinstallaties (RWZI’s), toestroming vanuit het buitenland en inlaat vanuit rijkswateren. Voor stikstof heeft actuele bemesting een groot aandeel (72%) in de uit- en afspoeling. Voor fosfor is dit aandeel kleiner (gemiddeld 33%). Binnen debeheersgebieden van de vier waterschappen zijn er per vanggebied grote verschillen tussen de belasting en herkomst. Enerzijds door de regionale verschillen tussen de af- en uitspoeling en het aandeel van de bemesting hierin, anderzijds door de lozingslocaties van RWZI’s, de toestroom vanuit het buitenland, inlaat vanuit rijkswater en de doorvoer van bovenstrooms gelegen waterlichamen, hetgeen sterk verschilt per gebied. Deze resultaten bieden de basis om scenario’s voor maatregelen op te stellen en effecten ervan op de waterkwaliteit te kwantificeren.
Light-dark rhythms during incubation of broiler chicken embryos and their effects on embryonic and post hatch leg bone development
Pol, C.W. van der; Roovert-Reijrink, Inge Van; Maatjens, C.M. ; Gussekloo, S.W.S. ; Kranenbarg, S. ; Wijnen, H.J. ; Pieters, R.P.M. ; Schipper, H. ; Kemp, B. ; Brand, H. van den - \ 2019
PLoS ONE (2019). - ISSN 1932-6203 - 17 p.
There are indications that lighting schedules applied during incubation can affect leg health at hatching and during rearing. The current experiment studied effects of lighting schedule: continuous light (24L), 12 hours of light, followed by 12 hours of darkness (12L:12D), or continuous darkness (24D) throughout incubation of broiler chicken eggs on the development and strength of leg bones, and the role of selected hormones in bone development. In the tibiatarsus and femur, growth and ossification during incubation and size and microstructure at day (D)0, D21, and D35 post hatching were measured. Plasma melatonin, growth hormone, and IGF-I were determined perinatally. Incidence of tibial dyschondroplasia, a leg pathology resulting from poor ossification at the bone’s epiphyseal plates, was determined at slaughter on D35. 24L resulted in lower embryonic ossification at embryonic day (E)13 and E14, and lower femur length, and lower tibiatarsus weight, length, cortical area, second moment of area around the minor axis, and mean cortical thickness at hatching on D0 compared to 12L:12D especially. Results were long term, with lower femur weight and tibiatarsus length, cortical and medullary area of the tibiatarsus, and second moment of area around the minor axis, and a higher incidence of tibial dyschondroplasia for 24L. Growth hormone at D0 was higher for 24D than for 12L:12D, with 24L intermediate, but plasma melatonin and IGF-I did not differ between treatments, and the role of plasma melatonin, IGF-I, and growth hormone in this process was therefore not clear. To conclude, in the current experiment, 24L during incubation of chicken eggs had a detrimental effect on embryonic leg bone development and later life leg bone strength compared to 24D and 12L:12D, while the light-dark rhythm of 12L:12D may have a stimulating effect on leg health.
Tissue specific expression and genomic organization of bitter sesquiterpene lactone biosynthesis in Cichorium intybus L. (Asteraceae)
Bogdanovic, Milica ; Cankar, K. ; Todorovic, Sladana ; Dragicevic, Milan ; Simonovic, Ana ; Houwelingen, A.M.M.L. van; Schijlen, E.G.W.M. ; Schipper, A. ; Gagneul, David ; Hendriks, Theo ; Quillet, Marie-Christine ; Bouwmeester, H.J. ; Bosch, H.J. ; Beekwilder, M.J. - \ 2019
Industrial Crops and Products 129 (2019). - ISSN 0926-6690 - p. 253 - 260.
Chicory (Cichorium intybus L.) produces bitter sesquiterpene lactones (STLs). Some enzymes in the biosynthetic pathway towards these compounds have been characterized. However, the genomic organization and tissue specificity of their biosynthesis is largely unknown. Concentrations of two sesquiterpene lactones and expression of genes involved in the first dedicated biosynthetic step were measured in different chicory tissues. BAC clones containing different genes encoding germacrene A synthase were sequenced, and revealed several tightly linked paralogs. Promoters of genes encoding two germacrene A synthases were fused to GFP and expressed in plants regenerated from transformed chicory hairy root cultures. Highest expression was observed in the epidermis of
leaves and external root tissue. This work opens the possibility to select for chicory germplasm diversified in STL content, and to study their role in chicory in defence and physiology.
Functional interpretation of the force-transmitting structures in a tree frog's toe pad
Langowski, J.K.A. ; Schipper, H. ; Berg, Frank van den; Blij, Anne ; Gussekloo, S.W.S. ; Leeuwen, J.L. van - \ 2018
In: SEB Florence 2018 abstract book 2: Animal biology abstracts. - - p. 152 - 152.
The morphology of tree frogs’ toe pads is adapted towards attachment, allowing these animals to move through their arboreal habitat. Whereas the superficial pad morphology has been studied extensively in previous research, little is known about the internal pad morphology and its functional relevance in attachment. We present the results of a 3-D characterisation and functional analysis of the internal toe pad morphology in the tree frog Hyla cinerea, combining histology, immunohistochemistry, synchrotron micro-computer-tomography, and finite element analysis. The morphology of force-transmitting pad structures, in particular of a collagen layer connecting the ventral epidermis with the medial phalanx, agrees in several aspects with the geometry of a pad model that is topologically optimised towards shear loading. This suggests that tree frogs’ toe pads are primarily adapted towards the transmission of shear loads, as experienced by the frogs while hanging on a vertical substrate. A collagenous septum running from the distal tip of the distal phalanx to the ventral cutis may play a role in peeling and detachment. Furthermore, we show that the adhesive toe pads of tree frogs contain smooth muscle fibre bundles with yet unknown functionality. Overall, our study contributes to the functional understanding of tree frog attachment, hence offering novel perspectives on the ecology, phylogeny, and evolution of anurans, as well as the design of tree-frog-inspired adhesives for technological applications.
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